Immunization phenomenon may be more effective by means of delivering antigens directly to the cells which are actively involved in presenting antigen such as macrophages and dendritic cells. Alternatively antigens delivered to follicular dendritic cells, may indirectly access B and T cells. We propose to develop recombinant antibody-antigen fusion's to specifically target antigens to these cells in vivo. Vehicles for cell specific delivery of protein antigens to these cells may enhance the immunogenicity or bias the TH1 versus TH2 response. The ability to target antigen directly to the follicular dendritic cells (FDC) may facilitate setting up an antigen depot by an alternative pathway. The fusion antigen in the proposed study is the carboxyl domain of circumsporozoite surface protein of the rodent malaria pathogen Plasmodium yoelii. (PyCSP). We propose to create Fab targeting antigen fusion/s with the carboxyl domain of PyCSP, which contains both athe CTL epitope and the hepatocyte binding region. Humoral and cellular response in mice immunized with the Fab fusions's will be evaluated. These recombinant antibody molecules may be useful in targeting a variety of epitopes to these cells. They may also be used to target athe delivery of synthetic particles encapsulating nucleic acids or nucleic acids directly. The ability to target molecules to these compartments may permit the elucidation of the role of these cells in an immune response. This study will increase our understanding of how these different antigen handling cells exert their effect on the immune system . Secondly these experiments will provide important information leading to better strategies for the development of vaccines.